Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753809AbbELTG5 (ORCPT ); Tue, 12 May 2015 15:06:57 -0400 Received: from saturn.retrosnub.co.uk ([178.18.118.26]:54595 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753408AbbELTGx (ORCPT ); Tue, 12 May 2015 15:06:53 -0400 Message-ID: <55524F4C.90604@kernel.org> Date: Tue, 12 May 2015 20:06:52 +0100 From: Jonathan Cameron User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Lars-Peter Clausen , Robert Dolca , linux-iio@vger.kernel.org CC: linux-kernel@vger.kernel.org, Hartmut Knaack , Peter Meerwald , Denis CIOCCA Subject: Re: [PATCH RFC 1/3] iio: Add symlink to triggers in the device's trigger folder References: <1429174868-11953-1-git-send-email-robert.dolca@intel.com> <1429174868-11953-2-git-send-email-robert.dolca@intel.com> <554CD236.4000404@kernel.org> <555230B0.3050700@metafoo.de> In-Reply-To: <555230B0.3050700@metafoo.de> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2382 Lines: 46 On 12/05/15 17:56, Lars-Peter Clausen wrote: > On 05/08/2015 05:11 PM, Jonathan Cameron wrote: >> On 16/04/15 05:01, Robert Dolca wrote: >>> This patch adds a new function called iio_trigger_register_with_dev >>> which is a wrapper for iio_trigger_register. Besides the iio_trigger >>> struct this function requires iio_dev struct. It adds the trigger in >>> the device's trigger list and saves a reference to the device in the >>> trigger's struct. >>> >>> When the device is registered, in the trigger folder of the device >>> (where current_trigger file resides) a symlink is being created for >>> each trigger that was registered width iio_trigger_register_with_dev. >>> >>> # ls -l /sys/bus/iio/devices/iio:device0/trigger/ >>> total 0 >>> -rw-r--r-- 1 root root 4096 Apr 16 08:33 current_trigger >>> lrwxrwxrwx 1 root root 0 Apr 16 08:33 trigger0 -> ../../trigg >>> er0 >>> >>> This should be used for device specific triggers. Doing this the user space >>> applications can figure out what if the trigger registered by a specific device >>> and what should they write in the current_trigger file. Currently some >>> applications rely on the trigger name and this does not always work. >>> >>> This implementation assumes that the trigger is registered before the device is >>> registered. If the order is not this the symlink will not be created but >>> everything else will work as before. >>> >>> Signed-off-by: Robert Dolca >> I was rather hoping we'd get a few more comments on this. >> In principle I like the idea, but it's new ABI and does make life >> a tiny bit more complex, so what do people think? >> >> Few trivial code comments inline. > > I don't think it adds more information. Both the trigger and the > device get registered for the same parent device, so you can already > easily find the trigger for a device by going to the parent device > and taking a look at the triggers registered by the parent device. I had the same thought. The question is whether the slightly gain in simplicity for userspace is worth it... I'm undecided at the moment. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/